Advanced Super Dimension Switching (ADS) liquid crystal display (LCD) is used to increase light transmittance of the LCD device across a plane. A multi-dimensional electric field is formed with both an electric field produced at edges of slit electrodes in the same plane and an electric field produced between a slit electrode layer and a plate-like electrode layer, so that liquid crystal molecules at all orientations, which are located directly above the electrodes and between the slit electrodes in a liquid crystal cell, can be rotated, which enhances the work efficiency of liquid crystals and increases the light transmittance. The Advanced Super Dimensional Switching technology can improve the image quality of thin film transistor liquid crystal displays (TFT-LCDs) and has advantages of high transmittance, wide viewing angle, high aperture ratio, low chromatic aberration, being free of push Mura, etc.
For the conventional ADS mode TFT-LCD, there is an angle between the rubbing direction of the alignment film and the horizontal direction. When the TFT-LCD is powered off, most of the liquid crystal molecules in the liquid crystal layer are arranged in the rubbing direction of the alignment film, thereby a good dark state is maintained. However, when the TFT-LCD is powered on, due to wires (such as data lines, gate lines and the like) and electrodes (such as source electrode, gate electrode and the like) existing at the edge of the pixel unit, a relatively complex electric field may be generated among those wires and electrodes, and in this case, the liquid crystal molecules at the edge of the pixel unit may be arranged according to the direction of this electric field but not the rubbing direction of the alignment film.
As shown in FIG. 1, a TFT array substrate 1 comprises a gate line 11 and a data line 12 intersecting with each other to define a pixel unit, a pixel electrode 13 in the pixel unit, and a common electrode 14 with slits. A relatively complex electric field may be generated among the gate line 11, the data line 12, the pixel electrode 13 and the common electrode 14. Under the effect of this electric field, the liquid crystal molecules in the region A of FIG. 1 may be arranged according to the direction of this electric field but not according to the rubbing direction of the alignment film. Thus, when the TFT-LCD is powered on, it may not be avoided that light leakage under dark state occurs in the region A.